Isolation of target cells or molecules from heterogeneous samples remains a prominent interest for research applications as well as medical applications, such as diagnostics and therapeutics. In particular, separation of rare cell types from physiological tissues and bodily fluids obviates the need to obtain large tissue samples and avoids the risks associated with the procedures required to obtain such samples. For example, isolation of fetal cells from maternal blood samples for genetic testing avoids the risks associated with aminocentesis or chronic villus sampling. Isolation of circulating tumor cells from a patient would allow the clinician to evaluate the cancer and monitor pathological changes in the patient's tumor, as well as evaluate the efficacy of any on-going drug treatments without conducting invasive biopsy procedures.
Current methods for separating biological molecules and/or cells from heterogeneous samples typically entail the use of a high affinity binding partner (e.g. an antibody or antigen) coupled to a solid support. The heterogeneous sample is passed over the solid support and the target biological molecules or cells of interest are bound by the binding partner and retained on the solid support. The bound molecules or cells of interest can be subsequently analyzed for the presence of molecular genomic and proteomic information.
These current approaches suffer from several technical difficulties, one of which is the problem of non-specific binding. To minimize non-specific binding, one or more washing steps is required to remove other molecules and/or cells that are bound to the solid support or binding partner. In addition, the subsequent in situ analysis of cells on the channel by staining and hybridization procedures may subject the cells to harsh and denaturing conditions. These washing and analysis procedures can compromise the initial capture of the desired molecule or cell by subjecting the binding partner to conditions that may cause the binding partner to degrade, lose some of its conformational structure, or become detached from the solid support.
Further still, existing methods for analyzing circulating cells (e.g., as captured from a patient sample) for malignancy, such as staining cells for cytokeratin (CK), have limitations as markers for identifying and/or evaluating circulating tumor cells.
Thus, there is a need in the art for additional methods and devices for isolating biological molecules and/or cells of interest from samples, as well as methods for subsequent analysis of captured targets, such as analysis of captured, circulating tumor cells.